The present invention relates to a multilayered polymeric body which reflects light and which can be fabricated to have a silvery or hued (i.e., copper, gold, etc.) metallic or nonconventional hued (i.e., blue, green, etc.) appearance, and to articles produced therefrom which may find use as mirrors, reflectors, lenses, polarizers, and the like.
Highly reflective articles (i.e., articles having a reflectance of 70-85% or greater) are generally sought by industry for a number of uses. Conventional methods for fabricating reflective surfaces include forming such surfaces of highly polished metals. Because of the high costs and fabricating problems involved in using metals, more recently fabricators have used plastic surfaces which contain thin coatings of metal thereon. Thus, metal coated plastic articles are now commonly found as both decorative and functional items in a number of industries. Such articles are used as bright work for consumer appliances such as refrigerators, dishwashers, washers, dryers, radios, and the like. These types of articles are also used by the automotive industry as head lamp reflectors, bezels, radio knobs, automotive trim, and the like.
Typically, such metal coated plastic articles are formed by electroplating or by the vacuum, vapor, or chemical deposition of a thin metal layer on the surface of the article. Such coatings are subject to the chipping and flaking of the metal coatings as well as corrosion of the metal over time. If additional protective layers must be applied over the metal coating to protect it, additional labor and materials costs are involved. Further, there may be environmental disposal problems with some metal deposition processes.
Multilayer articles of polymers are known, as are methods and apparatuses for making such articles. For example, such multilayered articles may be prepared utilizing multilayer coextrusion devices as described in commonly-assigned U.S. Pat. Nos. 3,773,882 and 3,884,606 to Schrenk. Such devices are capable of simultaneously extruding diverse thermoplastic polymeric materials in substantially uniform layer thicknesses. The number of layers may be multiplied by the use of a device as described in commonly-assigned U.S. Pat. No. 3,759,647 to Schrenk et al.
Im et al, U.S. Pat. No. 4,540,623, teach a multilayer laminated article which includes a polycarbonate as one of the alternating layers. The articles of Im et al, however, are intended to be transparent rather than reflective and to exhibit optical properties comparable to a pure polycarbonate polymer.
Alfrey, Jr. et al, U.S. Pat. No 3,711,176, teach a multilayered highly reflective thermoplastic body fabricated using thin film techniques. That is, the reflective thin film layers of Alfrey, Jr. et al relied on the constructive interference of light to produce reflected visible, ultraviolet, or infrared portions of the electromagnetic spectrum. Such reflective thin films have found use in decorative items because of the iridescent reflective qualities of the film.
However, the films of Alfrey, Jr. et al are extremely sensitive to thickness changes, and it is characteristic of such films to exhibit streaks and spots of nonuniform color. Further, color reflected by such films is dependent on the angle of incidence of light impinging on the film. Thus, such films are not practical for uses which require uniformity of reflectivity. Moreover, such films are not practical to thermoform into articles as localized thinning of the layers during thermoforming causes alterations in the reflective characteristics of the films.
In addition to the problems discussed above, many reflective articles such as those used in the automotive industry are exposed to extreme environmental conditions and do not exhibit good weatherability or resistance to solvents. Further, many of the films used in the production of reflective articles exhibit poor ductility and are thus difficult to thermoform into articles.
Accordingly, there remains a need in the art for a polymeric reflective sheet or body which can be fabricated into relatively thick parts without alteration of the uniform reflective appearance of the material over a range of processing conditions and part geometry. Further, there is a need for a highly reflective polymeric sheet or body which can be post formed without alteration of the uniform reflective appearance of the material. Still further, there is a need for silvery or metallic appearing articles which do not use metal and which exhibit good ductility, good weatherability, and resistance to solvents.